A 3rd Generation (3G) radio access network usually uses a microwave or metropolitan area optical transport network for data transmission between a base station and a base station controller. The mainstream mobile operators in this industry, such as Vodafone and Orange, carry out the wireless operations mainly by constructing microwave networks or leasing the transport networks of fixed network operators. The base station accesses the leased metropolitan area optical transport network through microwave, then the data flows from base stations are aggregated in the leased metropolitan area optical transport network, and the aggregated data flows are transmitted to the base station controller through a high-speed link. According to the traffic model, because the base stations will not reach the flow peak simultaneously, an aggregation node (or transport gateway) may be added at the first-level access point of the microwave network to aggregate the radio service data by packet switching, thus implementing the multiplexing of bandwidth. Therefore, the use of a service aggregation gateway can obviously improve the multiplexing efficiency of flows among the base stations to save the costs of purchasing microwave devices or leasing a metropolitan area optical transport network.
A first solution of the prior art related to the invention implements the transmission of an IP data flow on the ATM bearer network by using the IP over ATM (IPoA) protocol.
Herein, the standard IPoA protocol may implement the transmission of an IP data flow on the ATM bearer network, namely, support the transmission of a data flow of an IP base station on the ATM bearer network. The networking scheme is illustrated in FIG. 1. An IP base station transmits a data flow to an ATM switch 1 through an access layer of the IP Metropolitan Area Network (MAN) and the ATM switch 1 aggregates the data flow to an IP interface provided by the ATM switch 1; and the ATM switch 1 encapsulates received IP packet into a cell by using the IPoA protocol for the transmission on the ATM network (FIG. 1 illustrates the aggregation layer of the metropolitan area access network). An ATM switch 2 receives the cell and finishes the inverse process of the ATM switch 1 to reassemble the cell and recover the IPoA payload, namely, an IP packet.
FIG. 2 illustrates conversion of a protocol stack bearer in the first solution of the prior art. As illustrated, the ATM switches 1 and 2 actually use a tunnel, namely, a virtual channel, on the ATM network, to bear the IP packet, thus implementing the transmission of the IP packet on the ATM bearer network.
The inventor finds at least the following weaknesses in the first solution of prior art during the implementation of the invention:
1. Two sets of conversion devices are required, which increases the cost.
2. According to the IPoA protocol, the IP packet needs to undergo IPoA encapsulation and a tail is added, which reduces the bearer efficiency. During the transmission, encapsulation layers are added, so the transmission efficiency is reduced.
A second solution of the prior art related to the invention implements the transmission of an ATM data flow on the IP bearer network by using the Pseudowire Emulation Edge-to-Edge (PWE3) technology.
FIG. 3 illustrates a networking scheme of the second solution of the prior art. As illustrated, an ATM base station transmits a data flow to PWE3 equipment 1 through the access layer of the ATM MAN. An access ATM network may be accessed by using Inverse Multiplexing for ATM (IMA) over E1/T1, or ATM over Synchronous Digital Hierarchy (SDH) and connected to an ATM interface provided by the PWE3 equipment 1. The PWE3 equipment 1 encapsulates a received ATM cell into an IP packet by using the PWE3 protocol for the transmission on the IP network (FIG. 3 illustrates the aggregation layer of a metropolitan area access network). PWE3 equipment 2 finishes the inverse process of the PWE3 equipment 1 to disassemble the received IP packet into a cell and send the cell to a base station controller.
FIG. 4 illustrates conversion of a protocol stack bearer corresponding to FIG. 3. As illustrated, it can be seen that the PWE3 equipments 1 and 2 actually use a tunnel, namely, a PWE, on the IP network, to bear an ATM cell, thus implementing the transmission of the ATM cell on the IP bearer network.
The inventor finds that the second solution of the prior art has the similar weaknesses with the first solution during the implementation of the invention:
1. Two sets of conversion devices are required, which increases the cost.
2. The bearer efficiency is low. Meanwhile, because encapsulation layers are added, the transmission efficiency is reduced.